Adds typechecking of return values

frog/lib/corelib_impl.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #library("dart:coreimpl");
 
 #source("../../corelib/src/implementation/dual_pivot_quicksort.dart");
 #source("../../corelib/src/implementation/duration_implementation.dart");
 #source("../../corelib/src/implementation/exceptions.dart");
 #source("../../corelib/src/implementation/future_implementation.dart");
@@ skipping 217 matching lines @@
 // We can't do it yet because we'd need a way to redirect the const
 // default constructor.
 // TODO(jimhug): One way to resolve this is to make the const constructor
 // very special in order for it to generate JS regex literals into the code
 // and then treat the constructor as a factory.
 class JSSyntaxRegExp implements RegExp {
   final String pattern;
   final bool multiLine;
   final bool ignoreCase;
 
-  const JSSyntaxRegExp(String pattern,
-      [bool multiLine = false, bool ignoreCase = false]):
-    this._create(pattern, (multiLine ? 'm' : '') + (ignoreCase ? 'i' : ''));
+  const JSSyntaxRegExp(String pattern, [bool multiLine, bool ignoreCase]):

[Jennifer Messerly, 2011/11/11 02:36:01]

this is an unrelated fix I noticed in co19 checked mode (which isn't running
yet, but anyway...)

"null" is allowed as the default arg & shouldn't cause a type error.

+    this._create(pattern,
+        (multiLine == true ? 'm' : '') + (ignoreCase == true ? 'i' : ''));
 
   const JSSyntaxRegExp._create(String pattern, String flags) native
     '''this.re = new RegExp(pattern, flags);
     this.pattern = pattern;
     this.multiLine = this.re.multiline;
     this.ignoreCase = this.re.ignoreCase;''';
 
   Match firstMatch(String str) native
   '''var m = this.re.exec(str);
   return m && new MatchImplementation(
@@ skipping 155 matching lines @@
     } else if (isNaN()) {
       if (other.isNaN()) {
         return 0;
       }
       return 1;
     } else {
       return -1;
     }
   }
 }